Basic Python Flow Control

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🔎 Click this Flow Control Demo to see the basic Python flow-control statements in action in Memory Graph Web Debugger.

Normally, Python executes statements from top to bottom, but with flow-control statements we can change this flow by skipping, repeating, and jumping:

🔀 An if statement selects a branch based on a condition. Keywords: if, elif, else

🔁 A while loop repeats code while a condition remains true. Keywords: while, break, continue

🔄 A for loop visits each value in a sequence in order. Keywords: for, in, break, continue

📞 A function call transfers control to a function. A return statement sends control back to the caller, possibly with a return value. Keywords: def, return

Two particularly useful loop statements are:

• break: jumps past the end of the loop, stopping the loop

• continue: jumps to the start of the next loop iteration

Watching the flow of execution through a program makes it easier to understand what the code is doing, and where a problem (bug) may be hiding so that you can fix it. This becomes increasingly important when we nest flow-control statements for example, by placing an if statement inside a while loop, or making a function call inside another function call.

Which flow-control statement did you find most confusing at first?

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